This invention relates to a plasma display panel, a method of manufacturing the same, and a display device using the same.
In present days, plasma display panels (xe2x80x9cPDP""sxe2x80x9d) are drawing special attention among flat-panel display techniques, because of reasons that they are capable of delivering a speedier display and a wider viewable angle as compared to liquid crystal panels, easy to upsize a screen, superior in display quality since they are of self-luminous type, and so forth.
In general, the PDP""s generate ultraviolet rays by gas discharge, and produce color display by exciting and illuminating phosphor with the ultraviolet rays. A PDP is provided with display cells divided by barrier ribs on a substrate, and phosphor layers are formed in the individual display cells.
In particular, a mainstream of the PDP""s at present is a surface-discharge type PDP of 3-electrode structure. The PDP is so constructed that two panels of glass substrates are arranged to face against each other.
A pair of display electrodes are formed side by side in parallel with each other on one of the glass substrates, and an address electrode, which extends in a direction traverse to the display electrodes, a barrier rib and a phosphor layer are formed on the other glass substrate. PDP""s suitable for color display are thus manufactured by adopting this structure, which allows a comparatively thick phosphor layer.
FIG. 30 illustrates an exploded perspective view of a surface-discharge type PDP of the prior art having a 3-electrode structure. Display electrodes consisting of a pair of scan electrode 41 and sustain electrode 42 are formed on a front substrate 10 (The substrate formed with these electrodes is hereinafter referred to as xe2x80x9cfront platexe2x80x9d). Other substrate 20 is provided with a barrier rib 21 with an overcoating layer 24 between them, and a phosphor layer 22 is formed on its surface including a rib surface of the barrier rib (The substrate formed with these layers is hereinafter referred to as xe2x80x9cback platexe2x80x9d).
An advantage of the above structure is that it is relatively easy to manufacture because of its very simple structure. Moreover, brightness of the display device can be increased, since a luminous surface can be viewed directly in addition to this structure, which allows an increase in thickness of the phosphor layer. Also, because the phosphor layer is arranged at a distance away from the scan electrode, degradation of the phosphor layer due to sustain discharge is reduced.
However, the foregoing structure of the prior art yet has problems that luminous efficiency of the display device is low, and the brightness is also low. Furthermore, degradation of the phosphor due to address discharge is another problem, since the phosphor layer exists in a path of the address discharge as well as vicinity of it. Moreover, if a distance between the address electrode and the scan electrode is increased in order to prevent degradation of the phosphor layer, a voltage for the address discharge needs to be increased, which causes a high-speed address driving difficulty due to a delay in discharge. Further, the increase in voltage of the address discharge leads to other problems such as that it becomes liable to an erroneous discharge between neighboring cells, and so forth. On the other hand, if the distance between the address electrode and the scan electrode is shortened, degradation of the phosphor layer due to the sustain discharge becomes a serious problem. Also, thickness of the phosphor layer can not be increased in order to improve the brightness, since an increase in thickness of the phosphor layer inevitably reduces the discharge space.
Numerous studies have been done heretofore on every problems described above.
Japanese Patent Laid-Open Publication, number H05-121002 discloses a structure, in which phosphor is coated on both of a substrate facing against another substrate at a surface-discharge electrode side and an area of the another substrate in a discharge gap between the surface-discharge electrodes. Also, Japanese Patent Laid-Open Publication, number H05-299022 discloses another structure, in which phosphor is applied on nearly entire rib within a unitary emission unit including a side of a barrier rib and a surface of an address electrode. And, Japanese Patent Laid-Open Publication, number H06-243789 discloses yet another structure, which provides a barrier rib on a back plate approximately perpendicularly, and a phosphor layer on a surface of the barrier rib, wherein this phosphor layer is formed in a manner to taper off gradually. It describes that the structure allows a thick form of phosphor layer without sacrificing an area of discharge space. Further, Japanese Patent Laid-Open Publication, number H07-37511 shows a structure characterized by a phosphor layer, of which a surface is formed with bumps and dips. In addition, the same publication discloses that sides of a barrier rib are formed with bumps and dips, and the phosphor layer covers them uniformly. Furthermore, Japanese Patent Laid-Open Publications, numbers H08-222134, H09-199029, etc. indicate other attempts for increasing surface area of the phosphor layer by devising means of forming the phosphor layer.
There is also Japanese Patent Laid-Open Publication, number H06-44907 for an invention aimed at attempting to reduce a writing voltage, and to increase speediness and certainty of writing. Teaching of the publication, number H06-44907 is to expand an area of a portion of data electrode that faces against a scan electrode, so as to increase a contribution of the data electrode to a writing discharge.
However, the foregoing techniques of the prior art have not realized a PDP having a phosphor layer of high brightness and high luminous efficiency with less degradation of the brightness for a long-term operation, and yet capable of being driven at a high speed.
Furthermore, PDP""s of the prior art also have another problem concerning a white balance. It is generally desirable for PDP""s to have white color of high color temperature (10,000-9,000K) in the market. In order to produce white color of such a high color temperature, however, it is necessary to increase brightness of blue color comparatively high among those of three colors (red, green and blue). On the contrary, there is a limited variety of phosphor of blue color, and their brightness has not reached to a satisfactory level. Therefore, white balance is normally maintained by suppressing green color, which is high in visibility, by taking certain measures on a driving circuit, and increasing a luminous intensity of blue color, which is low in visibility. As a consequence, brightness of the PDP""s decreases further. However, it is the present situation that inventions have not sufficiently accomplished heretofore an improvement of white balance without reducing brightness of the PDP""s.
As another problem of PDP""s of the prior art, they consume ineffectual power, because a pair of display electrodes 41 and 42 are formed on either a same plane of a substrate 10 or a same plane that is generally in parallel with the substrate 10. The ineffectual power will be described now briefly. In an AC PDP, an electrode, a dielectric layer, a protective layer are normally arranged in a manner to face against each other across a discharge space or in a same surface plane, or in the like manner. Ultraviolet rays are generated by gas discharge in the discharge space, and the ultraviolet rays excite phosphor layer to produce a color display. Therefore, the AC PDP has a function of capacitor between the pair of display electrodes 41 and 42. That is, the PDP consumes ineffectual power by repeating a charge and a discharge of the capacitor, when a voltage is applied alternately between the pair of display electrodes 41 and 42, even if a gas discharge does not occur.
The foregoing will be described here in detail by referring to FIG. 31. In the AC PDP, there are a path 1 not passing through the discharge space and a path 2 through the discharge space between the pair of display electrodes 41 and 42. Therefore, a sum of two capacitances of a capacitor 1 formed by the path 1 and a capacitor 2 formed by the path 2 determines a capacitance of overall capacitors. It is only a charge and discharge of the capacitor 2 that contributes to the gas discharge, but a charge and discharge of the capacitor 1 does not contribute to the gas discharge, out of a charge and discharge of the overall capacitors. Therefore, an electric power consumed for charging and discharging the capacitor 1 becomes ineffectual power. The smaller the ineffectual power becomes, the better it is.
The following inventions disclose attempts to reduce consumption of electric power.
An invention disclosed by Japanese Patent Laid-Open Publication, number H07-226164 is a structure, which provides a first dielectric layer and another dielectric layer for accumulating a wall electric charge, one after another, on a display electrode, and the first dielectric layer is built to such height that it protrudes toward a discharge space higher than the display electrode. In addition, the first dielectric layer and the dielectric layer for accumulating wall electric charge are made so that the former has a low dielectric constant, and the latter has a high dielectric constant. There are also Japanese Patent Laid-Open Publications, numbers H07-111135 and H07-262930 for similar inventions. Also, an invention of Japanese Patent Laid-Open Publication, number H07-37511 is a structure, in which a first electrode driven by a single driver circuit is arranged between second electrodes, a plurality of which are successively switched and driven one after another. However, none of the foregoing examples of the prior art has achieved a sufficient reduction of power consumption.
In order to solve the foregoing problems, an object of the present invention is to provide a plasma display panel of high brightness and high luminous efficiency without causing a degradation of phosphor, as well as having a high speed and stable writing characteristic, a method of manufacturing the same, and a display device using the same.
Another object of the present invention is to provide a PDP that can display white color of high color temperature, a method of manufacturing the same, and a display device using the same.
Still another object of the present invention is to provide a PDP of high efficiency with a reduced ineffectual power that does not contributes to gas discharge, a method of manufacturing the same, and a display device using the same.
A plasma display panel (xe2x80x9cPDPxe2x80x9d) of the present invention comprises:
a pair of display electrodes formed on a first substrate of a pair of substrates sandwiching a discharge space between them;
an address electrode formed on a second substrate in a direction traverse to the paired display electrodes;
a barrier rib dividing the discharge space into individual unitary emission units; and
a phosphor layer,
wherein the PDP has a protrusion formed on an inner surface of the second substrate in a height lower than the barrier rib, and the phosphor layer is formed on a rib surface within the unitary emission units of the second substrate including a surface of the protrusion.
Also, a PDP of the present invention comprises:
a first electrode formed on an inner surface of one of a pair of substrates sandwiching a discharge space between them;
a second electrode formed on an inner surface of a second substrate in a direction traverse to the first electrode;
a barrier rib dividing the discharge space into individual unitary emission units; and
a phosphor layer,
wherein the PDP has a protrusion formed on the inner surface of the second substrate in a height lower than the barrier rib, and
further wherein the second electrode is provided on an upper part of the protrusion, and the phosphor layer is formed on a rib surface within the unitary emission units including the protrusion.
Further, a PDP of the present invention is characterized by controlling a luminous balance of individual colors (red, green and blue) of the phosphor layer by a shape of the protrusion. This enables the PDP to increase whiteness of a display without reducing a luminous efficiency.
Furthermore, a PDP of the present invention is a surface-discharge type plasma display panel comprising:
a pair of display electrodes formed on an inner surface of a first substrate of a pair of substrates sandwiching a discharge space between them; and
a dielectric layer and a protective layer formed, one after another, on the paired display electrodes,
wherein a part of an inner surface of the first substrate is opened to the discharge space either directly or through the protective layer.
Accordingly, the foregoing structures enable the PDP to reduce ineffectual power and to substantially improve efficiency.
In addition, the present invention is characterized by forming a gradually sloped surface at a distal end in a longitudinal direction of a protrusion during a process of manufacturing the PDP of the present invention. This structure realizes formation of an electrode line steadily on an upper part of the protrusion, thereby achieving a reduction of address voltage.
In the foregoing teaching of the present invention, the protrusion is meant to be a portion that extrudes partially, and that its shape, location and quantity are not restrictive. The same also applies to its material.